Some designs of wireless communication devices—such as smart phones, tablet computers, and laptop computers—contain one or more Subscriber Identity Module (SIM) cards that provide users with access to multiple separate mobile telephony networks. Examples of mobile telephony networks include Third Generation (3G), Fourth Generation (4G), Long Term Evolution (LTE), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division Synchronous CDMA (TD-SCDMA), Global System for Mobile Communications (GSM), and Universal Mobile Telecommunications Systems (UMTS).
A wireless communication device that includes one or more SIMs and connects to two or more separate mobile telephony networks using one or more shared radio frequency (RF) resources/radios may be termed a multi-SIM multi-standby (MSMS) communication device. One example is a dual-SIM dual standby (DSDS) communication device, which includes two SIM cards supporting two subscriptions that are each associated with a separate radio access technology (RAT) sharing on RF resource. In DSDS communication devices, the separate subscriptions share the one RF resource to communicate with two separate mobile telephony networks on behalf of their respective subscriptions.